The short answer is that Jupiter isn't big enough. Hydrogen on the Sun isn't "burning" as we know it -- that would combine with oxygen and release water. There's no oxygen at the Sun. Its mass and resulting gravity cause the hydrogen to begin fusing into helium, which is an exothermic reaction.

So for Jupiter to ignite we'd need to increase its mass by about three orders of magnitude (Jupiter is about 1.9*10^27 kg, the Sun is about 1.9*10^30 kg). This sounds simple enough, we just need to find some more Jupiter-stuff and throw it on the pile, right?

Your math is correct, IG.... *if* you are wanting Jupiter to be a sun-like
star.

If you'd settle for something smaller, it turns out that the requirement
for Jupiter to "become" a star (self sustaining hydrogen fusion reaction in
its core) is lots less. 8 Jovian masses does the trick.

I don't hate solar power itself, I hate people who ignore its lack of scalability
relative to conventional sources of energy and try to tax them into price
parity. That's not the same thing.

Ok, so Jupiter * 8 == star. How long would the reaction last, though, if
we only gave it the bare minimum mass?

In any case, I'm glad we have a physicist here in the pub with us, and not
a cosmologist. Cosmologists are morons who make stuff up. A particularly
stupid one named Stephen Hawking just said this week that you can pass through
a black hole and come out in another universe. Yeah, I saw that movie 36
years ago. He then went on to say that if something goes into a black hole,
it turns into a hologram. You cannot make this crap up! I wonder if he's
trying to out-moron Dawkins and Tyson.

I'd have to go and dust off the math to get a precise answer on the expected
lifetime of a star starting life with 8 Jovian masses. Off the top of my head
a good guestimate would be 800 million to 1.5 billion years.

The smaller the initial mass of any star, the longer it spends before becoming
a dwarf. In this case, it would 'almost' be a dwarf at birth.

The dwarf lifetime of a small mass star is hugely long. Again, if I remember
this 40-plus years ago exposure to the thermonuclear "chain of events" in
a small mass decaying star. There is no nova event; and certainly no supernova
event - these are what speeds up the end-stage of most stars. It won't even
do the "red giant" thing - not enough mass. It will die a very very slow and
very very boring death. Which, strange as it may seem, is ideal for the concept
of Jovian moons developing life. They'd have, as we would say in Philly,
"ooh-gobs" of time in which to do that!!

But Jupiter itself is nowhere near massive enough for that stuff. Any life
developing on Io or Europa will have to do that on its own (or have help from
The Monolith!!)<evil grin>.